FIG. 6 is a block diagram of a conventional high-frequency signal receiver. The receiver includes input terminal 1 for receiving a high-frequency signal, input circuit 2 to receive the signal received at input terminal, mixer 3 for receiving an output from input circuit 2 at its first input port, and for receiving an output from local oscillator 4 at its second input port, and filter 5 for receiving an output from mixer 3, second mixer 7 for receiving an output from filter 5 at its first input port and for receiving an output from second local oscillator 6 at its second input port, demodulator 8 for receiving an output from second mixer 7, phase locked loop (PLL) circuit 10 loop-coupled to local oscillator 4, and crystal oscillator 11 coupled to PLL circuit 10. The circuits are formed of unbalanced circuits, and, as shown in FIG. 7, are partitioned by metal partition plates 12 and covered by metal frame 13.
In the conventional receiver discussed above, harmonics of an oscillation signal of crystal oscillator 11 may enter into mixer 3, filter 5 or input circuit 2. To prevent an interference due to the signal, the circuits are placed apart from each other at an adequate distance, or local oscillator 4, PLL circuit 10, and crystal oscillator 11 are partitioned with metal plates 12 and covered with metal frame 13. Those measures against the interference cause the receiver to become bulky.